aacenc: Write correct length for long identification strings.

When the length is the escape value (15), the new length is calculated by
15 + get_bits(8) - 1.
Signed-off-by: NAlex Converse <alex.converse@gmail.com>

libavcodec/aacenc.c

@@ -462,7 +462,7 @@ static void put_bitstream_info(AVCodecContext *avctx, AACEncContext *s,
     put_bits(&s->pb, 3, TYPE_FIL);
     put_bits(&s->pb, 4, FFMIN(namelen, 15));
     if (namelen >= 15)
-        put_bits(&s->pb, 8, namelen - 16);
+        put_bits(&s->pb, 8, namelen - 14);
     put_bits(&s->pb, 4, 0); //extension type - filler
     padbits = 8 - (put_bits_count(&s->pb) & 7);
     avpriv_align_put_bits(&s->pb);